Carsharing, or car sharing, is a model of car rental where people rent cars for short periods of time, often by the hour. They are attractive to modern customers who may temporarily use a vehicle as well as to others who would like occasional access to a vehicle of a different type than they use day to day. The organization renting the cars may be a commercial business or users who are organized as a democratically controlled company, public agency, cooperative, or an ad hoc grouping. Carsharing contributes to sustainable transportation because it is a less car intensive means of urban transport. Carsharing has been said to reduce car ownership at an estimated rate of one rental car per 15 owned vehicles.